


theoretically speaking

by wbtrashking (fan_nerd)



Category: Fullmetal Alchemist - All Media Types, Fullmetal Alchemist: Brotherhood & Manga
Genre: Established Relationship, Fluffy Smut, M/M, PWP, Post-Canon, Technobabble
Language: English
Status: Completed
Published: 2017-08-03
Updated: 2017-08-03
Packaged: 2018-12-10 04:23:29
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,924
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11683986
Author URL: https://archiveofourown.org/users/fan_nerd/pseuds/wbtrashking
Summary: Edward smirks brightly, his rant about the finer points of alchemical theory coming to a halt. "Oh my fucking god," he exclaims, "You totally get off on this."Roy groans.





	theoretically speaking

**Author's Note:**

> it's 3:30 in the morning, it's been a hell of a day, and i'm rewatching fma:b because i'm a glutton for punishment. this fic takes place after the events of the fma manga/brotherhood anime, but there's not many spoilers bc this is just some light hearted fluff and i'm a softy.
> 
> this is a ridiculous fic, and i seriously loved writing every quip. enjoy. ♥

The two of them have an arrangement. The terms are clearly stated: Edward is allowed to roam all over the world as he freely pleases, research to his heart's content, and has a key to Roy's home - _their_ home - so that he has a place to return to whenever he finds himself in Central. Their relationship is no secret; Roy knows that threatening Edward at gunpoint wouldn't have done a damn thing to keep his mouth shut, so the moment that Ed had propositioned him, as a young man fresh from the road and a clean breakup with his childhood friend, he'd made moves to announce this change between them in a happy manner for the government.

It's not as if homosexuality is particularly frowned upon in Amestris. Of all the fucked up things this country has named to its' legacy, that portion, at least, is one that Roy and Edward can proudly say has been a boon, and they intend to protect their rights as a powerful open couple within its' borders.

And thus, many years after the Promised Day, Edward trudges into their house with mud on his boots, fire in his golden eyes, and he grabs Roy's attention as he throws his suitcase to the wayside and flops onto the couch. He says nothing before he kicks off his shoes and awkwardly plops onto Roy's lap, his teeth flashing up at his partner. "Heya."

Roy can already tell, by the pleasant energy nearly vibrating off of Edward's skin, that he's eager to rant about whatever clue it is that he's discovered out on the road, but before the younger man can speak, he softly kisses him on the brow. "Welcome home, Edward."

"Thanks," the blonde flatly replies. Roy rolls his eyes at the blasé tone - he'd expected nothing less from him, naturally. "Okay, so, remember last time, when I was trying to figure out why there were so many varying definitions to alkahestral symbols and I was trying to understand how important grounding objects were?"

Roy's answer to Edward's inquiry is  _vaguely_ , but then again, he'd been half-asleep when Edward had rambled about this on his last visit home, holding the blonde's hand and murmuring as he'd spoken. As it stands, it's not as though the blonde is looking for a reply - he's going to keep on trudging through his explanation anyhow, so Roy just hums in reply and sort of zones out.

Edward is truly a sight when he gets all worked up like this. His hair is long and sun-streaked in different hues of gold; his jaw strong, his chin thoughtlessly shaved. Really, it's the passion in his voice that's captivating, his arms flying to and fro as he rambles, pressed against Roy in each jostling moment, so enthralled with fresh knowledge that he glows with pleasure. It's only natural, really, after so many months apart that he reacts to beauty of the man's physical presence. He'd rather not interrupt Edward, however; he just lets his skin grow unpleasantly hot and curses himself for having such a reaction - and at  _his_ age, no less - so he just cards a hand through the end of Ed's ponytail and studies his young lover fondly.

Suddenly, he's not speaking, and Roy is terrified that Edward is going to move away from him and chastise Roy for not paying attention.

Instead, the look that crosses his face is far from disdainful. He looks like a playful cat, canines particularly sharp as his lips curve upwards, and he brusquely puts one of his hands over Roy's crotch, earning a hiss from the brunette.

Edward smirks brightly, his rant about the finer points of alchemical theory coming to a halt. "Oh my fucking god," he exclaims, "You totally get off on this."

Roy groans.

"I'm not  _getting off_ on this, as you've so eloquently put it," Roy grumbles, although his protest is feeble. "I'm just...appreciating the sound of your voice while you recount your discoveries."

"Excuses," Edward purrs, sitting up and moving so that he can seat himself in Roy's lap and tangle his fingers in the older man's hair. He musses it, because he dislikes seeing Roy's bangs pushed back when they're alone. "You like it when I talk all scientific and shit? Want me to recite fundamentals and do equations while I fuck you or something?"

The blonde rolls his hips and Roy  _hates_ how easily Edward gets under his skin - how very, very well his old subordinate knows him, even after all this time. "You're the genius between the two of us, aren't you? Why wouldn't you make the obvious assumption and say that I've just missed hearing you be pain in the ass?"

"Pain in your ass, specifically, as often as I can manage it," Edward tosses the quip Roy's way as he kisses him, hot and open-mouthed and full of tongue, so filthy in his movements that Roy can't help shifting against him, both of them moaning and reluctant to pull apart, even to breathe. "Missed you too, old man."

"And who says you're fucking me tonight?" Roy tries to sound reproachful, but mostly he sounds pretty desperate.

Because he is. _Totally_ desperate.

"Tally's even," Edward says, so matter of fact as he starts to peel off Roy's layers of clothing that his older lover almost misses his lack of patience as a child and willingness to fall for Roy's cruel façade. Now, this creature - so comfortable in his own skin that he's licking his lips in anticipation - is as foreign and familiar as he ever was, and Roy loves it. It's horrid, how very deep his affection runs. "I came home with all the new knowledge and shit, so I get to wow you with it while I work you open, and you repay the favor tomorrow morning by bending me over the kitchen table or something."

Edward, even freed from all his chains and curses of the past, is such a stringent subscriber of equivalent exchange that Roy could strangle him.

When he imagines all of the ways Edward's mouth will be occupied in the next hour, both with words and with Roy's body, his skin trills and he knows Edward has won the battle before it's begun.

He's also a glutton for punishment and a slave to pleasure, so of course he just leans into Edward's nape and puts on an air of being put off by the notion for all of two minutes before Edward scoops him into his arms and drags him upstairs to the bedroom. "The thing about translating symbols is that over time, things get lost, which is fuckin' obvious, duh, but a lot of people forget how dependent on oral tradition and pictography the kingdom of Xing is." His breath is hot as he undresses Roy slowly, fingers prying the buttons off of Roy's evening clothes and delighting as the older man inadvertently shivers at the touch. "The foundation of the Amestrian alphabet is fairly recent - the country was founded less than four hundred years ago, after all, so all of the cultural differences have made the alkahestral symbols far more widespread and open to interpretation than the alchemical ones."

Roy bites his lips to keep from growling at Edward, hot in Edward's calloused palms as the younger man begins to stroke his dick. When he's finally focused enough to speak, he bites out, "You tease."

Without acknowledging that Roy had spoken, he arches sideways on the mattress to rifle through the nightstand for lubricant, and he circles his fingers at Roy's entrance with unrestrained glee. "So, of course, once I start cracking the codes between all of the varying interpretations - and don't forget, they've had clan wars for  _centuries_ \- then I start looking into to theoretical principles behind all of the shit, yeah? Imagine, we're talking  _ridiculous_ shit. Air-distanced traveling, the power of the dragon cycles, or whatever, bursting at the seams of  _every_ citizen, and so forth. Frankly dangerous bullshit, but hey. That shit follows me around like a curse. I  _had_ to develop circles for as much as I could possibly fathom, even if I can't seem to  _do_ jack shit with them yet."

He has three sun-kissed fingers deep up his old superior's  _ass_ , has ignored Roy's breathless pleas for Edward to _shut up and fuck me_ three times, and, as much as Roy's dick is supremely interested in hearing Edward ramble on and on, leaking and threatening to come, Roy has had  _enough_.

"Edward," he hisses dangerously, bucking back against the blonde in a way that he knows will finally get the menace to be quiet. "C'mon, Edward, I'm ready, _please_." He hates begging, and Edward knows it, but he needs this - he's burning to have more of Edward inside of him, instead of the glances of the pads of Edward's fingers over his prostate. "More talking later."

Edward smirks and shucks off his pants -  _finally_ \- and he breathes in the musky scent of Roy's backside as he grabs more lube. "Impatient fucker," Edward murmurs, but the words are fond and Roy's cheeks are far too flushed for his responding glare to carry heat. "You want me to fuck you that badly? So badly that you'd rather me do that than keep making you harder, so hard you can't fucking handle it? Want me to fuck you and finally stop making it ache?"

Roy could kill him. Before he snarls out something witty in response, Edward grabs his hips sharply and drills into him, and Roy changes his mind - he  _will_ kill Edward, just as soon as he can stop moaning like a dying man, clutching the sheets to gain his bearing. Edward's lips course over his shoulders gently as he leans back and thrusts in again. "Fuck," Roy exhales slowly, trying hard not to let his tongue loll at the sensation.

"Currently doing that," Edward replies, but his tone is distracted, if a bit smug. "Feel good, Mustang?"

"Fantastic," Roy earnestly offers the praise, and helplessly curls further into himself when Edward adjusts his position and the tip of his cock presses hard against Roy's prostate. "Okay -  _really fantastic._ Hell. I missed you."

There is nothing but the sound of skin slapping skin and pants for a long moment, and Roy wonders if that had been the wrong thing to say. Then, Edward finally says, "Missed you too, asshole," and his fingers move from bracing Roy's hips to caressing his strong forearms and momentarily tweaking his nipples. "Missed this. Missed having you tight around me, trying to talk shit, but too full of my dick to do anything other than squirm and push back against me."

The laughter that strikes out of Roy's throat rumbles through both of their bodies and Edward chuckles deeply in response. "Cocky little shit."

"I resent the  _little_ part," Edward quips back before pressing his teeth sharply into Roy's neck and resting there for some time; long enough to leave a purpling hickey that will tell the whole office exactly who had wandered back into Central.

Neither of them speak after that - the rush is too heady. Roy grabs for one of Edward's hands - both flesh, and what a glory they are, so strong and sturdy and beautiful that Roy could wax poetic about them all night - and kisses his tan knuckles. "Are you close?" He breathes the question, though he already knows the question.

"Real close," Edward dutifully responds, curling his fingers around Roy's, resting their hands on Roy's straining right thigh. "Want you to come first though."

Roy's laugh is desperate and lacking air. He's been on the edge the whole evening, and he's certain that he'd  _already_ come, just minutes ago. Edward is a demanding lover. "Alright then," Roy acquiesces easily, watching the blonde flick deft fingers over his length. He pushes himself deep into Roy as he pulls the brunette off, kissing his back and murmuring under his breath, although whether he's cursing or praising Roy, Roy himself has no idea.

He comes with a sharp awareness of how much the sensation makes his back arch, and he feels Edward pull out of him to come, semen slipping down his thighs in a small spurt.

_Brat._

Since Roy is always far too exhausted to move after they have sex, Edward moves around like the hurricane that he is, moving to get a warm, wet towel from the device that he and Roy had crafted together, just for moments like this. It has a series of transmutation circles carved onto it to make the temperature perfect and keep their house from catching fire; beyond that, for holding moisture, and keeping the cloth in tact. Edward thinks it is pretentious, hilarious, and wonderful. He would never let Roy get rid of it.

As he always does, he carefully maps the planes of both of their bodies, noting the healed scars ambling over their forms. Their trousers are due for a hearty wash in the morning, so he bundles them into a ball and tosses them into a hamper before lying beside Roy, finally divesting himself of the rest of his own clothing and smiling fondly after he's wiped both of their arms, legs, and crotches off.

"Was it really just the talking that did it for you?" Edward is a scientist through and through and Roy can't help snickering at his genuinely curious tone. " _What?_ I mean, it's not like I mind or anything. What's new, you kinky fuck? First it was my hair, then it was my ability to haul your ass up with one arm, then it was how flexible I was...it's not like finding out that you're attracted to me doing more weird shit is like, news."

Roy finds himself unable to stop laughing for a time. "I suppose you're correct. You're a very attractive, if infuriating, person." Before Edward can even snort at the  _infuriating_ bit, Roy continues, "That's why I love you, though. Always something new for me to discover as well."

Edward rolls his eyes. "It's amazing that you got into office with all that fucking schmoozy talk. More people oughtta smell your bullshit from a mile away."

Führer Roy Mustang, elected just two years ago, rolls his eyes right back. "Yes, well, lucky for both of us that most people  _enjoy_ my _schmoozy_   _talk_ , as you've so eloquently put it." He curls fingers in Edward's twisting blonde hair, pulling the strands free from his ponytail at long last. "And by the way, I believe you owe me ten thousand cenz and my jacket back. I  _told_ you that those reforms for schools in Drachma were going to go well if I sent Alphonse there to be my liaison, and lo and behold."

The blonde grumbles. "Fuck you. Using Al is against the rules."

"In your own words, you said that you were going to keep paying me back and asking more and more of me. I suppose it says quite a lot of me that I'm not only looking forward to what, exactly, you've done with my coat, but also that I'm dying to know what you'll be asking for next."

"I'll tell you after breakfast tomorrow," Edward promises, interlacing his and Roy's hands over his abdomen, relishing in Roy's warmth, even though he knows he's in for a long lecture in the morning, among many other things. "You know. Once you've had your turn."

Roy's lips curl up against the skin of Edward's neck and Edward valiantly resists scowling in response. "Will you be here for some time?"

"Few weeks," Edward says, moving from the tight embrace to grab the duvet from the floor and toss it over them, and sliding right back into Roy's arms. "Give or take."

"Good," Roy happily exhales. "Who says that I want to wait until the morning to have my turn?"

The blonde snorts at that, noting that Roy's fingers are dancing from their soft, chaste hold at his abdomen and are tickling the soft skin of his flesh leg. "Need me to start reciting fundamental theories to get you hard, old man?"

"You're too observant and mouthy for your own good, brat," Roy murmurs back, and he delights when Edward arches back against him, toes curling. "Who says that I can't get  _you_ off by talking about my intellectual pursuits and political intrigue?"

He can, is the thing.

Edward had admitted as much with a heavy blush, citing that he'd loved the thick tone to all of Roy's words when he talked about his progress at work, feeling invigorated to prove that he  _had_ done many great things in this broken nation. He loves that. Roy feeling  _powerful_ , feeling comfortable enough to boast when Roy is fucking him.

Both of them grin and moan, scrambling to toss off the covers and shut each other up.

In the morning, when Riza knocks at the door and Edward answers, she's only grateful that the both of them have on clothes, and that Roy has already eaten breakfast.

The whole office rejoices and whistles when Roy enters, fresh-faced and crisp, wondering when they'll be able to call Ed around for drinks, and he quiets them swiftly, nearly ordering his whole team to get to work.

He's going to enjoy his time alone with Ed  _thoroughly_ before Edward starts wandering all over town to meet up with old friends.

They only have so much time to figure out these new obsessions with each other, after all.


End file.
